AUGUSTA — The Maine Department of Transportation (DOT) is proposing that the Maine State Ferry Service be allowed to impose a surcharge on “any and all” fares if it experiences “increases in the operating costs … and/or decreases in ridership.”

That is a provision of a proposed rule on rates for ferry service between the mainland and six offshore islands, including Swan’s Island and Frenchboro. A public hearing on the proposed new rule was scheduled for Nov. 28 in Belfast.

Myron “Sonny” Sprague, chairman of the Swan’s Island Board of Selectmen and a member of the Ferry Service’s advisory board, said he planned to speak at the hearing.

“I think part of my testimony and that of others will be that we don’t know if this [possible future surcharge] is going to be 2 percent or 50 percent and that there should be a cap on it and that the Maine State Ferry Service advisory board should be involved,” Sprague said. “There should be some controls. [The DOT] shouldn’t be able to [raise fares] automatically without oversight from the advisory board.”

Sprague said he didn’t think the proposed rule that would allow the ferry service to raise rates without any guidelines, limits or oversight was written by ferry service or DOT officials.

“I think you’ll find they gave it to a lawyer, and this was kind of the first draft before someone cuts it to pieces,” he said.

In May, the department implemented a standardized fare structure that eliminated what DOT Commissioner David Bernhardt described as “the antiquated and geographically discriminatory rate pricing that currently differs from island to island and island to mainland.”

The new rate structure also was designed to increase overall revenue by about $740,000 a year, which would allow the ferry service to generate at least half of its annual operating budget of roughly $11 million, as required by state law. The other half of the money comes from the state’s highway fund.

One of the biggest changes in the ferry rate structure was the elimination of deeply discounted prices for tickets bought on the outer islands. Previously, people who bought round-trip tickets on the islands paid just over half as much as the price of tickets on the mainland.

Ferry service officials said many people, including those who live on the islands only in the summer, had been taking advantage of what was intended as a benefit to year-round island residents by purchasing their ferry tickets on the islands. They said 80 percent of all ticket sales had been occurring on the islands, depriving the ferry service of much-needed revenue.

For residents of some of the islands served by the Maine State Ferry Service, most of the new rates that went into effect in May were not seen as overly burdensome.

For example, a round-trip ticket for a private vehicle between Swan’s Island and Bass Harbor, which previously cost $27.25 if purchased on the island, now costs $30, regardless of where it is purchased.

But on the Lincolnville to Islesboro route, the ferry service’s most heavily traveled, the round-trip fare for a private vehicle more than doubled, from $13.50 to $30.

On May 23, the town of Islesboro asked the Kennebec County Superior Court to stay implementation of the new rates pending the outcome of an appeal. Town officials claimed the new rates were excessive and unfair.

In a ruling issued Nov. 2, Judge Michaela Murphy wrote, “Islesboro has shown neither irreparable injury nor that substantial harm to the public will occur if the stay is granted. Accordingly, Islesboro’s motion for a stay is denied.”

However, the judge found that the new ferry rate schedule was “not determined through a process that was consistent with the requirements for rulemaking as set forth in the Maine Administrative Procedure Act.”

As a result of that finding, the DOT now proposes to use the proper rulemaking process to adopt the same fare schedule it implemented in May, but with the addition of the provision allowing it to increase any ferry fares at any time if revenues do not keep up with operating costs.

In addition to Swan’s Island, Frenchboro and Islesboro, the state-operated ferries serve the island towns of North Haven, Vinalhaven and Matinicus. The ferry terminals on the mainland are in Bass Harbor, Lincolnville and Rockland.